The present invention is generally related to window coverings and is more specifically related to cordless blinds for covering window openings.
Window blinds are typically used for covering window openings. The blinds are usually moveable between an open position so that light may pass through the window and a lowered or closed position in which the window blind at least partially blocks the passage of light. A closed window blind also provides privacy so that individuals outside a building may not look into a building. Most window blinds include a lifting cord which passes through an aperture in each of the slats or through a window covering material such as cellular or pleated shades.
There have been many improvements related to cordless window blinds. Such improvements attempt to simplify the process of operating a window blind and facilitate cleaning of the blind.
For example, U.S. Pat. No. 1,798,869 discloses in FIG. 1 a headrail for a Venetian blind including a traversing rod 16 to which there is attached a pair of lift cords 20, 21. U.S. Pat. No. 1,978,152 discloses a blind incorporating a traversing rod 1 from which there is supported a plurality of slats. Referring to FIG. 6 of the '152 patent, the traversing rod may be operated by a hand crank assembly 23 that is coupled via rod 19 to an end of the traversing rod by means of a gear assembly (FIG. 3).
U.S. Pat. No. 5,318,090 is directed to a roller assembly for a Venetian blind. Referring to FIG. 1 thereof, the roller assembly includes an elongated driving member 62 having a circular axial hole 623 extending through a rectangular shaft section 621. The shaft section is received within the end portion of a rotating rod 50. A guide unit 63 includes a threaded rod 633 extending through the circular axial hole of the driving member and into engagement with a moveable member 61 that is fixed in an intermediate position within the rotating rod. A lift cord is coupled to a portion of the driving member to rotate same in either a clockwise or counterclockwise direction. When the lift cord is pulled, the driving member rotates the rotating rod to move the moveable member along the threaded rod of the guide unit, thereby both rotating and moving the rotating rod along the guide unit.
U.S. Pat. No. RE 35,926 is directed to a Venetian or pleated blind that is adapted to be positioned between a pair of glass panes. Referring to FIGS. 1 and 2 thereof, the blind includes a housing having two corner spacer elements 26, 32 attached to opposite ends of the headrail housing. Each of the corner spacer elements are attached to respective adjacent side spacer elements 60, 62 on each side of the window. The headrail defined by housing elements 4, 8 includes a traversing rod 16 referred to in the claims as a winding shaft.
U.S. Pat. No. 5,482,100 is directed to a blind including at least one constant variable spring force motor having an elongated spring. The spring has a generally rectangular cross-section which varies in width from one end to the other. The varying spring force is sufficient to maintain the bottom rail in any position with respect to the top rail as the shade material accumulates on the bottom rail when moving the bottom rail towards the headrail.
U.S. Pat. No. 5,531,257 is directed to a cordless blind having a spring motor coupled to an electronic motor. The electronic motor and the spring motor rotate a cord spool to raise or lower the window covering.
U.S. Pat. No. 6,234,236 discloses a cordless window covering system incorporating a plurality of spring motors that are coupled together. Referring to the figures, the system includes at least two springs motors 40 in combination with a coupler 62, 62A. The coupler connects the spring motors together to have a combined spring force. In other embodiments, the pair of spring motors are coupled together and attached to the lift cords.
U.S. Pat. No. 6,079,471 teaches a window covering including a friction imparting member to inhibit movement of the bottom rail. Referring to FIG. 2 thereof, the friction and parting member includes a bracket 55 having a plurality of slots 56 that are used to increase the tension on cord 52 traveling through hole 50 in surface 47 towards the cord spool 30.
U.S. Pat. No. 6,129,131 is generally directed to a blind system including a traversing rod 32 coupled to a pull system 38 that imparts uni-directional movement to the coupling drive shaft 40. The pull system includes a one-way clutch assembly 50 and a main drive assembly 42 including a single pull tape 46 operative of a drive spool 48. The brake arm 150 is adapted to selectively prevent or permit lowering of the shade by gravity. The traversing assembly includes a compression spring 210 having one end slidably engaged with a disc-shaped end 220 of the cord spool 206. The other end of the compression spring is attached to a spring support spool that is rotatable by the drive shaft. The compression spring is relatively light, but strong enough to push the cord spool to the left when no counterforces exist.
Three related patents, U.S. Pat. Nos. 5,813,447; 5,960,846 and 6,047,759 all teach a window shade incorporating an internal spring tensioning mechanism. The spring tensioning mechanism is adapted for tensioning the spring upon rotation of the shade bar in one direction and releasing the spring tension upon opposite shade bar rotation, with the releasing of the spring force accomplished by a manual force rotating the shade bar in the tensioning direction.
Despite the above improvement, there remains a need for improved cordless blind assemblies.